DNA replication is the process of copying single or double-stranded DNA. Because DNA strands are antiparallel and complementary, each strand may serve as a template for the reproduction of the opposite strand by a DNA polymerase. The template strand is preserved as a whole or as a truncated portion and the new strand is assembled from nucleoside triphosphates.
In polymerase chain reaction (PCR), the target DNA, a pair of primers, and a DNA polymerase are combined and subjected to repeated temperature changes that permit melting, annealing, and elongation steps. The melting or denaturation step typically occurs at a high temperature limiting the choice of polymerases to thermophilic polymerases.
Endonuclease V (also called endo V or inosine 3′ endonuclease) is a DNA repair enzyme first described in E. coli that recognizes DNA containing nucleotides with deaminated or otherwise modified bases such as inosine. Endonuclease V cleaves the second or third phosphodiester bond 3′ to the inosine in the same strand leaving a nick with 3′-hydroxyl and 5′-phosphate. DNA polymerases add nucleotides to the 3′ end of a pre-existing DNA strand resulting in 5′→3′ elongation in a template-directed fashion to create a complementary strand.